Apple admitted battery-life problems with the iPhone 4S and the new iOS 5 earlier this month, and released the iOS 5.0.1 update on Thursday. Many users, however, report that the fix either didn't help or made matters worse.

We've followed the whole battery usage sage since it began here. A good round up of the situation until yesterday is here. However, while the update, from iOS 5.0.0 to 5.0.1 is supposed to address this issue from the look of the Apple forums it's not doing this quite perfectly in every case:

Yesterday I upgraded to 5.0.1 and now battery life is SIGNIFICANTLY WORSE. Yesterday 20 min of web surfing took it down 1%. This morning, after the upgrade last night, 20 min of surfing took it down 10%. That's 10 times worse!

I upgraded my iphone 4S to the 5.0.1 release today. However, I've noticed that my battery life has actually gotten worse since I upgrade. For example, I've been home for approximately 30 minutes and my battery has gone down in 8%. In the 30 minutes, I had a 30 second phone call and sent 3 text messages. I am connected to our wi-fi (which is a strong connection) and I have re-started my phone.

However, as The Register points out, this absolutely isn't true of all who have made the upgrade. For some (many perhaps, those who have had a problem fixed are likely to be less vocal than those still with a problem) the upgrade has fixed all of the problems just fine. Which makes the issue one a little tricky for Apple itself:

The fact that some iPhone 4S users presumably had their battery problems fixed by the iOS 5.0.1 upgrade, some have not, and some report that their problems have become worse, points to the possibility that the problem may be more hardware-related – which would, of course, be a far more expensive problem for Apple to address than a simple iOS upgrade.

If all of the hardware is exactly the same then the reaction of every piece of hardware to a change in the software should be the same. Which leaves us with two possibilities as to why some phones are fixed, some are not and some are made worse by the OS upgrade.

The first is relatively benign: there's some mixture of apps running or of software configurations that leads to battery drainage. Perhaps, as was originally thought, multiple attempts to synchronise databases or something. This will get pretty much sorted out through the user experience one would think.

However, there's another possible explanation: the different reactions to the same software indicate that the hardware is not exactly the same underneath. Given the volumes produced there might be multi-manufacturer sourcing going on, not of assembly, but perhaps of certain components. And perhaps some but not all of those different combinations of components are causing the problem. Pure and entire speculation, of course, but potentially a much more expensive problem to solve.